Decouple integer formatting from std::num::strconv

This works towards a complete rewrite and ultimate removal of the `std::num::strconv` module (see #6220), and the removal of the `ToStrRadix` trait in favour of using the `std::fmt` functionality directly. This should make for a cleaner API, encourage less allocation, and make the implementation far more comprehensible.

The `Formatter::pad_integral` method has also been refactored make it easier to understand.

The formatting tests for integers have been moved out of `run-pass/ifmt.rs` in order to provide more immediate feedback when building using `make check-stage2-std NO_REBUILD=1`.

The benchmarks have been standardised between std::num::strconv and std::num::fmt to make it easier to compare the performance of the different implementations.

Arbitrary radixes are now easier to use in format strings. For example:

~~~
assert_eq!(format!("{:04}", radix(3, 2)), ~"0011");
~~~

2 files changed, 88 insertions, 18 deletions

diff --git a/src/libstd/num/mod.rs b/src/libstd/num/mod.rs
index 767faa30f24..150c7bdab29 100644
--- a/src/libstd/num/mod.rs
+++ b/src/libstd/num/mod.rs
@@ -22,6 +22,7 @@ use mem::size_of;
 use ops::{Add, Sub, Mul, Div, Rem, Neg};
 use ops::{Not, BitAnd, BitOr, BitXor, Shl, Shr};
 use option::{Option, Some, None};
+use fmt::{Show, Binary, Octal, LowerHex, UpperHex};
 
 pub mod strconv;
 
@@ -278,7 +279,12 @@ pub trait Int: Integer
              + CheckedAdd
              + CheckedSub
              + CheckedMul
-             + CheckedDiv {}
+             + CheckedDiv
+             + Show
+             + Binary
+             + Octal
+             + LowerHex
+             + UpperHex {}
 
 /// Returns the smallest power of 2 greater than or equal to `n`.
 #[inline]
diff --git a/src/libstd/num/strconv.rs b/src/libstd/num/strconv.rs
index 6be829f51d7..c0c3074be63 100644
--- a/src/libstd/num/strconv.rs
+++ b/src/libstd/num/strconv.rs
@@ -804,24 +804,88 @@ mod test {
 #[cfg(test)]
 mod bench {
     extern crate test;
-    use self::test::BenchHarness;
-    use rand::{XorShiftRng, Rng};
-    use to_str::ToStr;
-    use f64;
-
-    #[bench]
-    fn uint_to_str_rand(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
-        bh.iter(|| {
-            rng.gen::<uint>().to_str();
-        })
+
+    mod uint {
+        use super::test::BenchHarness;
+        use rand::{XorShiftRng, Rng};
+        use num::ToStrRadix;
+
+        #[bench]
+        fn to_str_bin(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<uint>().to_str_radix(2); })
+        }
+
+        #[bench]
+        fn to_str_oct(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<uint>().to_str_radix(8); })
+        }
+
+        #[bench]
+        fn to_str_dec(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<uint>().to_str_radix(10); })
+        }
+
+        #[bench]
+        fn to_str_hex(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<uint>().to_str_radix(16); })
+        }
+
+        #[bench]
+        fn to_str_base_36(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<uint>().to_str_radix(36); })
+        }
     }
 
-    #[bench]
-    fn float_to_str_rand(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
-        bh.iter(|| {
-            f64::to_str(rng.gen());
-        })
+    mod int {
+        use super::test::BenchHarness;
+        use rand::{XorShiftRng, Rng};
+        use num::ToStrRadix;
+
+        #[bench]
+        fn to_str_bin(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<int>().to_str_radix(2); })
+        }
+
+        #[bench]
+        fn to_str_oct(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<int>().to_str_radix(8); })
+        }
+
+        #[bench]
+        fn to_str_dec(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<int>().to_str_radix(10); })
+        }
+
+        #[bench]
+        fn to_str_hex(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<int>().to_str_radix(16); })
+        }
+
+        #[bench]
+        fn to_str_base_36(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { rng.gen::<int>().to_str_radix(36); })
+        }
+    }
+
+    mod f64 {
+        use super::test::BenchHarness;
+        use rand::{XorShiftRng, Rng};
+        use f64;
+
+        #[bench]
+        fn float_to_str(bh: &mut BenchHarness) {
+            let mut rng = XorShiftRng::new();
+            bh.iter(|| { f64::to_str(rng.gen()); })
+        }
     }
 }